RATES OF HEAT AND WATER-LOSS IN FEMALE MINK (MUSTELA-VISON) MEASURED BY DIRECT CALORIMETRY

The energy expenditure (EE) of adult female mink was studied by contin uous 24-hr measurement of rates of total heat loss (THL) in a controll ed environment using a 24 m(3) calorimeter allowing separate on-line d etermination of sensitive (SHL) and evaporative (EHL) heat loss within the range of 20-200 W (72-720 kJ/hr). In four adult female mink (scan black colour mutant), studied in transparent cages and given free acce ss to feline food pellets and water, the mean 24-hr energy expenditure (=THL) under controlled experimental conditions was 8.9 W/kg (range: 5.5-13.1 W/kg) at 18 degrees C and 5.8 W/kg (range: 4.3-9.5 W/kg) at 2 4 degrees C. The results are in agreement with the data reported in th e literature on the metabolic rate of adult farm-raised mink, calculat ed from rates of oxygen uptake under controlled experimental condition s, and with the energy requirement for maintenance, 586 kJ/kg/day (6.8 W/kg) recommended by the NRC. Under the experimental conditions of th e present study the mean rate of total evaporative water loss (TEWL) a mounted to 3.7 g/kg/hr at 18 degrees C and 5.5 g/kg/hr at 24 degrees C . The contributions of SHL and EHL to 24-hr THL in female mink were in versely related and markedly dependent on chamber temperature. When co rrected for evaporated urinary and faecal water, SHL and EHL amounted to 76 and 24% of THL at 18 degrees C, but at 24 degrees C the correspo nding values were 41 and 59%. The mean rate of insensible water loss, calculated as total evaporative water loss minus faecal and urinary wa ter evaporated from the bedding material, amounted to about 84-90% of TEWL or 3.1 g/kg/hr at 18 degrees C and 5.0 g/kg/hr at 24 degrees C. T he increase of EE in response to ambient temperatures below the thermo neutral zone (''metabolic coefficient'') calculated from the differenc e between the minimum values for the EE at 18 and 24 degrees C amounte d to 0.20 W/degrees C/kg.